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HKAL Exercise : Part 3 Waves
Chapter 12 Optical Instrument
12.1 Reflection
Moving Mirrors
1. A plane mirror is rotating with angular
speed ω. When pulses of light, of pulse
frequency f, strike the mirror, they are
reflected such that the angle between
successive reflected pulses is θ. If the
direction of the incident pulses remains
constant, the value of θ is
A.
C.

.
f
2
.
f
B.
D.

.
2f
4
f
Concave Mirrors
3. The focal length of a concave mirror is f.
The mirror will produce a real, inverted
and magnified image when the distance of
the object from the pole of the mirror is
A. greater than 2f.
B. equal to 2f.
C. between f and 2f.
D.
less than f.
4.
.
concave
mirror
lamp
2.
The diagram shows a mirror M which
rotates about an axis through X with
constant angular velocity ω , and a
spherical mirror Y whose centre of
curvature is at X, where XY = r.
Y
r
M
X

A narrow parallel beam of light strikes M
at X, with angle of incidence θ, such that
it is reflected along XY, then along YX and
is again reflected by M, to form the
emergent beam. What is the angle between
the initial incident and final emergent
beams ? (c is the speed of light.)
A.
2r
c
B.
4r
c
C.
r
2c
D.
r
4c
HKAL Exercise Chapter 12 Optical Instrument
The diagram above shows a small electric
lamp fixed on a wall and positioned on the
principal axis of a concave mirror of
radius of curvature 9 cm. If the mirror is
18 cm from the wall, which of the
following statements best describes the
appearance of the reflected light on the
wall?
A. It is the form of a dot on the
lamp.
B. It is a circular patch round the
C.
D.
lamp and the same size as the
mirror.
It is a circular patch round the
lamp but larger in size than the
mirror.
It is a circular patch round the
lamp but smaller in size than the
mirror.
1/18
5.
parallel beam of light to be reflected from
M?
M
I
(1) replacing M by a concave mirror of
longer focal length
(2) moving the mirror M away from O
(3) placing a diverging lens of suitable
focal length between O and M
A. (1) only
B. (3) only
C. (1) and (3) only
D. (2) and (3) only
O
Rays from a point light source O are
reflected by concave mirror M and
converge to a point I as shown. Which of
the following operations would enable a
12.2 Refraction
6.
A beam of monochromatic light passes
through three media of refractive indexes
n1 , n2 and n3 respectively as shown. The
boundaries between the media are parallel.
8.
n1
n2
n3
Which of the following relations between
n1 , n2 and n3 is correct ?
A.
C.
n1 > n3 > n2
n2 > n1 > n3
B.
D.
n1 > n2 > n3
n3 > n2 > n1
When a parallel beam of white light passes
through a glass lens, it is separated into
rays of different colours. For which colour
of light does the lens have the greatest
focal length and for which colour of light
does glass have the greatest refractive
index ?
The lens has the Glass has the
greatest focal
greatest refractive
length for
index for
A.
B.
C.
C.
7.
orange light
orange light
green light
green light
blue light
yellow light
blue light
yellow light
0.1 m
0.1 m
When a pin is moved along the principal axis of
a small concave mirror, the image position
coincides with the object at a point 0.3 m from
the mirror. If the mirror is placed at a depth of
0.1 m in a transparent liquid, the same
phenomenon occurs when the pin is placed 0.2
m from the mirror. The refractive index of the
liquid is
A. 1.
B. 4/3.
C. 3/2.
D. 2.
HKAL Exercise Chapter 12 Optical Instrument
9.
When a diver looks up towards the surface
from underwater, the surface behaves like
A. a diverging lens.
B. a converging lens.
C.
D.
a plane mirror with a circular
hole in it, centred above the
diver’s head.
a circular plane mirror of limited
extent, centred above the diver’s
head.
2/18
Total Internal Reflection
10.
Prism
12.
i
M1
M2
v1
v2

i
Light travels in media M1 an M2 with
speeds v1 and v2 respectively. When light
travelling from medium M1 strikes a
boundary between the two media with
angle of incidence i, it suffers total internal
reflection. This indicates that
(1) sin i is less than v1/v2.
(2) sin i is less than v2/v1.
(3) v1 is less than v2.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (2) and (3) only
A ray of light passes through a prism as
shown. As the angle i is increased from
zero to 90∘, the angle θ
A.
passes through a maximum value.
B.
C.
D.
decreases continuously.
increases continuously.
remains constant.
13.
A
i
C
B
11.
When light is incident on the face AB of a
normal
air
water
ultra-sound
beam
A beam of ultrasound is being emitted
from a submarine under water towards the
water surface. Which of the following
statements is true?
A. The refracted beam leaving the
B.
C.
D.
surface will bend away from the
normal.
The refracted beam will travel
along the water surface.
The refracted beam will bend
towards the normal.
Total internal reflection will
occur.
HKAL Exercise Chapter 12 Optical Instrument
prism as shown, it may pass through the
face AC, with total deviation d, or it may
suffer total internal reflection at AC.
Which of the graphs below best represents
the variation of d with i? (t.i.r. represents
total internal reflection)
A.
B.
d
t.i.r.
0
d
t.i.r.
90O
t.i.r.
i
0
C.
D.
d
d
t.i.r.
0
90O
i
t.i.r.
90O
i
0
90O
i
3/18
14.
prism is filled with water, and light is
incident normally on the face XY. If the
X

refractive indices for water and glass are
4/3 and 15/8 respectively, total internal
reflection will occur at the glass-air
surface XZ only for sinθ greater than
glass
air
water
Y
Z
A.
C.
A glass vessel in the shape of a triangular
Convex Lens
15. The image of an object formed on a screen
by a thin converging lens has height a. By
1
ab
2
C.
a
b3
B.
ab
D.
b
a3
B.
D.
3/4.
32/45.
image at infinity. If the least distance of
distinct vision is 25 cm, the angular
moving the lens towards the screen, a
second lens position is found at which the
height of the image formed on the screen
is b. What is the height of the object ?
A.
2/5.
8/15.
magnification achieved is
A. 0
B. 1
C. 1.25
D. 25
18.
L
S
I
16. The image of an object formed on a screen
by a convex lens has height a. By moving
the lens towards the screen, it is found that
there is a second lens position at which
another image of height b is formed on the
screen. The height of the object is
A. (a + b)/2.
B. a2/b.
C.
b2/a.
D.
(ab) .
17.
20 cm
object
A converging lens of focal length 20 cm is
used as a magnifying glass with the final
HKAL Exercise Chapter 12 Optical Instrument
A converging lens L and a lamp S are
arranged as shown. The rays from S
converge at a point I after passing through
L. Which of the following operations
could enable a parallel beam of light to
emerge from the lens L?
(1) replacing L by a lens with less
converging power
(2) moving the lens L to the right until
parallel rays are obtained
(3) placing a diverging lens of suitable
focal length in front of the lens L
A. (1) only
B. (3) only
C. (1) and (2) only
D. (1) and (3) only
4/18
22. The sun subtends an angle of 1.5∘at the
19.
surface of the Earth. A convex lens of
L
focal length 300 cm is used to form an
image of the sun onto a screen. The
diameter of the image is about
A. 59 mm.
B. 79 mm.
C. 99 mm.
D. 200 mm.
I
O
A real image I of an object O is formed by
a converging lens L as shown above. A
diverging lens L1 is placed between L and
I such that a real image I’ is obtained.
Which of the following statements is/are
23. A real object is placed in front of a
concave mirror of focal length f. Real
images are formed by the concave mirror
for various object distances u. If the image
correct ?
(1) I’ is larger than I.
(2) I’ is further away from L than I.
(3) I’ is also an erect image.
A. (1) only
B. (1) and (2) only
C. (2) and (3) only
D. (1), (2) and (3)
distances are denoted by v, which of the
graphs below shows the variation of |v|
with |u| ?
A.
B.
|v|
|v|
|f|
|f|
|f|
20. When an object placed far away from a
concave mirror is gradually moved
towards the lens, the separation between
the object and its real image will
A. remain unchanged.
B. decrease.
C. decrease and then increase.
D. increase and then decrease.
21. The image of the moon is focused on a
screen by a converging lens of focal length
15 cm. If the moon subtends an angle of
7.5 × 10-3 radian at the centre of the lens,
calculate the diameter of the image.
A. 2.8 × 10-2 cm
B. 5.6 × 10-2 cm
C. 1.1 × 10-1 cm
D. 2.3 × 10-1 cm
|u|
C.
|f|
|u|
|f|
|u|
D.
|v|
|v|
|f|
|f|
|f|
|u|
24.
object
screen
lens
glass
slab
A converging lens forms a sharp image on
HKAL Exercise Chapter 12 Optical Instrument
5/18
a screen as shown. A glass slab of
thickness t is inserted between the lens and
B.
away from the lens; d is
independent of t.
the screen. In order for the image to be
again sharply focused, it is necessary to
move the screen a small distance d
A. towards the lens; d increases
when t increases.
C.
away from the lens; d decreases
when t increases.
away from the lens; d increases
when t increases.
Concave Lens
25. A train of plane wavefronts is incident
upon a diverging lens. F denotes one of
the focal points of the lens. Which of the
following diagrams represent(s) what
might happen to the wavefronts?
(1)
D.
26. Which of the following ray diagrams
is/are correct ? (F is the focus of the
corresponding optical instrument.)
(1)
(2)
F
A.
C.
D.
F
(3)
F
F
2F
(1) only
B.
(1) and (2) only
(2) and (3) only
2F
(2) only
27.
(2)
L
P
X
F
Q
Y
O
S
In the above figure, XY is the principal
axis of a lens L. PQ and OS are two
refracted rays from L which originate from
a point object placed on the left side of L.
Which of the following deductions is/are
correct ?
(3)
F
A.
B.
C.
D.
(1) only
(3) only
(1) and (3) only
(2) and (3) only
HKAL Exercise Chapter 12 Optical Instrument
(1) The image of the point object must be
virtual.
(2) The lens L must be a concave lens.
(3) The point object must lies alone the
line PQ.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (2) and (3) only
6/18
System of Lens and Mirrors
28.
30.
L2
L1
L
S
O
M
15 cm 15 cm 15 cm 15 cm
The diagram shows a converging lens L,
of focal length of magnitude F, a convex
mirror M of focal length of magnitude f,
and the position S at which an object is
coincident with its own image. If SL = x
The above diagram shows two light rays
from a point source O passing in turn
through a convex lens L1 and a concave
lens L2. Which of the following is true of
and LM = y, then
A. y + F = 2f.
the focal lengths of the lenses ?
Focal length of L1 Focal length of L2
A.
7.5 cm less than 15 cm
B.
15 cm
less than 15 cm
C.
7.5 cm greater than 15 cm
D.
15 cm
greater than 15 cm
1
B.
1 1 
x    
y F
C.
1 1 1
  .
x y F
D.
1
1
1

 .
x y2f F
 f .
31.
M
L
29.
O
M
L
I
4 cm
8 cm
4 cm
4 cm
A converging light beam is directed
towards a convex mirror M. The reflected
beam then passes through a convex lens L
and forms an image at I. Which of the
following about the focal lengths of M and
L is correct ?
focal length of M focal length of L
A.
more than 4 cm
2 cm
B.
more than 4 cm
4 cm
C.
less than 4 cm
2 cm
D.
4 cm
2 cm
HKAL Exercise Chapter 12 Optical Instrument
100 cm
A small object O is placed at the focus of a
convex lens L as shown. A concave mirror
M is placed 100 cm behind the lens. If the
focal length of L is 60 cm and the final
image formed by this system is at infinity,
the focal length of M is
A. 20 cm.
B. 40 cm.
C. 50 cm.
D. 80 cm.
7/18
32.
33.
L2
L1
L2
L1
O
30 cm
40 cm
L1 and L2 are converging lenses, each of
focal length 20 cm. The final image of
object O, formed by refraction through
both lenses, is at I. The distance OI is
A. 10 cm.
B.
C.
D.
60 cm.
80 cm.
90 cm.
50 cm
In the figure, L1 and L2 are two thin lenses with
the same focal length 60 cm placed coaxially
50 cm apart. A beam of light originating from a
distant object is incident on L1. Which of the
following statements about the final image
formed by the system of lenses is correct ?
A. It is virtual and formed between L and L2.
B. It is virtual and formed on the left of L1.
C. It is real and formed between L1 and L2.
D. It is real and formed on the right of L2.
12.3 Optical Instruments
EYE
(Essay 88:E2)
34. The human eye functions as a converging lens of variable focal length. Explain why the
apparent sizes of the Moon and a dollar held at arm’s length seem similar.
(2 marks)
35. A short-sighted person’s greatest distance of distinct vision is 0.7 m. His sight is improved by
wearing spectacles which increase his greatest distance of distinct vision to 15 m. What is the
magnitude of the focal length of the spectacle lenses?
A. 0.67 m.
B. 0.73 m.
C. 14.3 m.
D. 15.7 m.
Magnifying glass
(Essay 88:E2)
36. When a single converging lens is used as a magnifying glass the viewed image may be formed
at (a) infinity or (b) the distance of nearest clear vision from the eye.
Using a ray diagram show which of these arrangements gives the greatest magnification. What
is the physical factor limiting the magnification ?
(4 marks)
HKAL Exercise Chapter 12 Optical Instrument
8/18
37. A converging lens of focal length 15 cm is used as a magnifying glass with the final image
formed at infinity. If the least distance of distinct vision is 25 cm, the angular magnification is
A.
3/5.
B.
5/3.
C.
8/3.
D.
10/3.
38. An object placed in front of a magnifying glass forms an image at infinity with magnifying
power 5. What is the focal length of the magnifying glass ? (You may assume the least distance
of distinct vision to be 25 cm)
A. 125 cm
B. 25 cm
C. 5 cm
D. 4.3 cm
Compund Microscope
39 In a compound microscope,
(1) the final image produced is erect.
40.
E
(2) the final image produced is virtual.
(3) the focal lengths of both the objective
and the eyepiece must be short in
order to produce high magnification.
A. (1) only
B. (3) only
C. (1) and (2) only
D. (2) and (3) only
eyepiece
focal length fe
B
O
A
objective
focal length fo
The diagram represents a microscope with
the object at A. The image of A in the
objective is formed at B. Which of the
following statements is/are correct ?
(1) BE is larger than fe.
(2) AO is larger than f0.
(3) The image at B is virtual.
A. (1) only
B. (2) only
C. (1) and (2) only
D. (2) and (3) only
(Structural question 94:L2)
41. (a)
eyepiece
objective lens
object
h0
final
hi
image
P
Fo
Q
Fo FE
FE
Figure 41.1
A student uses two converging lenses to set up a compound microscope in normal
HKAL Exercise Chapter 12 Optical Instrument
9/18
adjustment. Figure 41.1 shows two light rays, P and Q, from the top of an object falling
on the objective lens of the microscope. The foci of the objective lens are denoted by FO
and the foci of the eyepiece are denoted by FE.
(i) On Figure 41.1, complete the ray paths for P and Q as they pass through the
microscope, showing how the final image is formed.
(2 marks)
(ii) Indicate on Figure 41.1 the visual angle β subtended by the final image at the eye
of an observer using the microscope.
(1 mark)
(iii) Distinguish between linear magnification and angular magnification.
(2 marks)
(iv) Find the angular magnification of the microscope in terms of the height of the object,
ho, and the height of the final image, hi. Show your working. (Take the least distance
of distinct vision to be D)
(2 marks)
(b) Figure 41.2 shows four light rays from an object passing through a microscope in normal
adjustment. R and S come from the top of the object, T and U come from the bottom. R
and T pass through the top of the objective lens, S and U pass through the bottom.
R
T
object
S
U
objective
lens
X
eyepiece
Figure 41.2
(i)
On Figure 41.2, X is the best position for the eye to view the image. With reference
to the ray diagram, briefly explain the advantage(s) of choosing X as the viewing
position.
(3 marks)
(ii) Why should the diameter of the beam at X be no wider than about 2 mm ? (1 mark)
HKAL Exercise Chapter 12 Optical Instrument
10/18
Refracting Telescope
42. An astronomical
telescope
has
an
objective of focal length 45 cm, and an
eyepiece of focal length 3 cm. It is used to
look at a distant object when its lenses are
set 48 cm apart. The final image seen is
A. inverted, virtual and at infinity.
B. inverted, real and at infinity.
C. upright, real and at infinity.
D. upright, virtual and at the least
distance of distinct vision.
42. In a simple astronomical telescope, under
normal adjustment, which of the following
statements is/are correct?
(1) The first image is formed at the focal
plane of the eyepiece.
(2) The focal length of the objective is
shorter than that of the eyepiece.
(3) The first image is real and inverted.
A. (1) only
B. (3) only
C. (1) and (3) only
D.
(2) and (3) only
43. An astronomical refracting telescope is
adjusted to view a distant object under
normal adjustment. Which of the
following statements is/are correct ?
(1) The final image formed by the
eyepiece is at the least distance of
distinct vision from the eye.
(2) The first image formed by the
objective is real and is smaller than
the object.
(3) If part of the objective is blocked by
an opaque obstacle, part of the final
image could not be viewed.
A. (2) only
B. (3) only
C. (1) and (2) only
D. (2) and (3) only
HKAL Exercise Chapter 12 Optical Instrument
44. Lens
I
II
III
IV
Nature
Focal length
converging
converging
diverging
diverging
10 cm
60 cm
10 cm
60 cm
A student is given the above 4 lenses, and
asked to make a telescope which will give
erect magnified final images. How should
he choose the lenses ?
objective
eyepiece
A.
B.
C.
D.
I
I
I
II
II
III
IV
III
45. In an astronomical telescope set at normal
adjustment, the focal lengths of the
objective and the eyepiece are 50 cm and
20 cm respectively. Which of the
following gives the separation of the
lenses and the angular magnification of
the telescope ?
Lens
Angular
Separation
magnification
A. 30 cm
0.25
B. 50 cm
0.25
C. 50 cm
2.5
D. 70 cm
2.5
46. A simple two-convex lens refracting
telescope has a magnifying power of 12
when the telescope is in normal
adjustment. The focal length of the
objective is 0.95 m. The separation
between the objective and the eye piece is
A. 0.08 m.
B. 0.87 m.
C. 1.03 m.
D. 12.4 m.
11/18
47. An astronomical refracting telescope
consists of two converging lenses of focal
lengths 100 cm and 10 cm. Under normal
adjustment, it is used to observe a distant
object which subtends an angle of 0.5∘
when viewed directly. Which of the
following statements is/are correct ?
(1) The height of the first image formed
by the telescope is 8.7 mm.
(2) The lens with focal length 100 cm
should be the eyepiece.
(3) The angle subtended by the final
image seen by the observer is 5∘.
A. (1) only
B. (3) only
C. (1) and (3) only
D. (2) and (3) only
48. The image of a distant star produced by an
astronomical telescope is a diffraction
pattern. If the effective diameter of the
objective lens is reduced to one-half by
covering its outer parts with a stop, the
49.
A distant object consisting of two arrows
is viewed through an astronomical
refracting telescope consisting of two
converging lenses. Which of the following
corresponds to the image seen ?
A.
B.
C.
D.
area of the central maximum of the
diffraction pattern is
A. halved.
B. doubled.
C. decreased by a factor of 4.
D. increased by a factor of 4.
Projector Lens
50. A projector lens produces a clear, enlarged image of a slide on a screen. How could a clear
image with greater magnification be obtained ?
screen
movement
lens movement
A. none
closer to the slide
B. closer
none
C. farther away closer to the slide
D. farther away none
HKAL Exercise Chapter 12 Optical Instrument
12/18
Reflecting Telescope
(Essay 98:E2)
51. (a) Explain what is meant by the normal adjustment for an astronomical refracting
telescope and why it is used in this way.
(2 marks)
(b) (i)
Draw a diagram to show the passage of three light rays passing through an
astronomical refracting telescope from a point on a distant object (not on the axis of
the telescope) when it is used with normal adjustment. Mark the foci of the objective
lens (Fo) and eyepiece (Fe) clearly on your diagram. State the functions of the
objective lens and eyepiece.
(ii) What is the meaning of the magnifying power of the astronomical refracting
telescope with normal adjustment ? State the ways of increasing the magnifying
power and discuss the limitations on its value.
(iii) What is the major disadvantage of the astronomical refracting telescope for viewing
objects on the ground ? With the help of a suitable diagram, show how this
disadvantage can be overcome.
(10 marks)
HKAL Exercise Chapter 12 Optical Instrument
13/18
(Essay 95:E5)
52. Describe an experiment for measuring the wavelength of monochromatic light using a
spectrometer and a diffraction grating with a known grating spacing.
(4 marks)
HKAL Exercise Chapter 12 Optical Instrument
14/18
HKAL Exercise (KEY) : Part 3 Waves
Chapter 12 Optical Instrument
1 – 10 : CBCCC, ADACB,
11 – 20 : CBBBB, DCDBC, 21 – 30 CBADC, BADAC,
31 – 33 : BCD,
34.
R
long distance
moon
L
dollar
O2

O1
a

b
image
1
The size of the image formed on the retina of the eye only depends upon the angle
subtended by the object at the eye.
1
This angle is similar for the larger object (moon) at a long distance and the smaller
object (dollar) at a nearer distance.
1
2
2
2
35 : B
36.

L
I'
h'
O'
I

h
F
O
'
C
D
1
Larger objects at a fixed distance will appear larger since the
angle subtended at eye is greater.
1
Clearly, from ray diagram, the viewed image I formed at the distance of nearest clear
vision D appears greater than the image I’ formed at infinity
since  > ’, and hence magnification is greater for the former arrangement.
Magnification is limited by the focal length of the lens.
1
1
2
+
1
2
2
2
14
37 – 40 : CCDB,
HKAL Exercise Chapter 12 Optical Instrument
15/18
41. (a) (i)
(ii)
2+1 3
eyepiece
objective lens
object
h0
final
hi
image
P
Q
Fo
(iii) Linear magnification
=
Angular magnification =
Fo FE 
FE
height of image
1
height of object
visual angle of the image
visual angle of the object
(iv) Without microscope, visual angle of the object  
With microscope, visual angle of the object  

angular magnification =
12
h0
D
h1
D
h

= 1

h0
(b) (i)
All the light from the objective lens (or the object) would pass through X.
The image is then brightest
And the field of view is greatest.
(ii) Matching the beam to the diameter of the pupil.
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1
1
13
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42 – 50 : ACAD, DCBCD,
51. (a) The telescope is in normal adjustment if the final image is at infinity, so that the
eye is in a fully relaxed state and the observer can view for long periods of time
without undue strain. (or so that the final image is at the position where the
observer expects to see it.)
(b) (i)
HKAL Exercise Chapter 12 Optical Instrument
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2
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Objective
L1
fo
Parallel rays
from point at
top of distant
object


Eyepiece
L
fe 2
Fe
Fo
h1 
I1
To top of final virtual
image at infinity
Objective lens is used to collect large amount of light from distant object
and to form a real intermediate image at its focal plane acting as an
1
1
2
2
object for the eyepiece.
Eyepiece acts as a magnifying glass for magnifying the intermediate real
1
2
image formed by the objective and produce a virtual image.
(ii) Magnifying power M is defined as M = β / α where
β = angle subtended at the eye by the final image at infinity
4
(i.e. visual angle of object with aided eye)
α = angle subtended at the eye by the object without the telescope
(i.e. visual angle of object with unaided eye)
1
Magnifying power can be increased by : using objective lens of longer focal length fo
using eyepiece of shorter focal length fe
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1
2
2
Limitations on magnifying power : fo cannot be too long as long tube length (fo + fe) will cause inconvenience. 1
fe cannot be too short as too curved lens causes spherical/chromatic
aberration.
(iii) One major disadvantage is that the final image observed is inverted.
Use an erecting lens (convex, focal length f) for an additional inversion
by placing it between the intermediate image and the eyepiece as shown.
The final image observed is erect and not laterally inverted.
HKAL Exercise Chapter 12 Optical Instrument
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1
2
2
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To top of final virtual
image at infinity
Eyepiece
Objective
Erecting
lens
Parallel rays
from point at
top of distant
object
I1
I2
fo
2f
2f
fe
1
or
(Arrange two totally reflecting prisms (45∘– 90∘– 45∘) between the
2
objective and eyepiece.)
52.
collimator
telescope
*
light
source
crosswire
platform
Usual adjustments are first made on (i) cross-wires, (ii) telescope and (iii) collimator
of the spectrometer so that the collimator produces parallel light and the telescope
focuses it at the cross-wires.
1
The table with the grating are turned so that the incident light falls on the grating normally.
The telescope is rotated, say to T1, and the reading corresponding to the first-order
image is taken.
The first-order reading on the other side of the normal, say at T2, is also taken.
incident
light
1
1
1
2
2
2
T1
grating


T2
Halve the angle between these two readings gives θ,
from which λ can be calculated using nλ = d sinθ
where d is the grating spacing and n = 1.
HKAL Exercise Chapter 12 Optical Instrument
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2
2
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